The present invention relates to a dispenser, especially a hand-held spray can in which a piston is advanced to eject a spray upon manual actuation of a valve.
Hand-held spray dispensers are conventional in which a piston is housed within a container below a product to be dispensed. By advancing the piston toward a valved end of the container, the product is forced through the valve.
In U.S. Pat. No. 3,195,168, an axially threaded rod is provided which extends axially within the container and carries a threaded follower. Disposed above the follower is a piston which seals against the inside surface of the contents chamber. The rod is rotated by means of a knob mounted at the bottom of the container. A spring disposed between the follower and piston transmits motion from the follower to the piston and stores energy. By rotating the rod, the follower and piston are raised to dispense the contents. Although the spring effectively stores energy, it does not transmit the energy to the piston as uniformly across the area of the piston as would be desired, thereby resulting in a less-than-optimum spray pattern.
It would be desirable to provide a relatively low-cost easily assembled, dispenser which makes it possible to store propulsion energy so that a continuous discharge can be effected with a highly uniform spray pattern.